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L0301P43 - Principles of Muscles and Joints
Types of Muscle *muscle is the only tissues in the body that can generate a force *smooth **controls blood vessels, lymphatics, internal sphincters, organs and “specialist tube” *cardiac **contracts the heart *skeletal **moves the body Smooth Muscle *non-striated *mononuclear, spindle shaped cells *involuntary contractions via intermediate filament bundles attached to dense bodies *found in: **sphincters, vessels wall **eyes, skin (hair) **respiratory, gastrointestinal, reproductive and urinary tracts Cardiac *striated *involuntary contractions **autonomic regulation *branching *mononuclear in adult human *longitudinally connected by intercalated discs **synchronised depolarisation *found in heart Skeletal Muscle *striated **at right angles to the line of contractions *longitudinal but no branching *multinucleated cells = mega cell *voluntary contractions **generates, control and/or limit movement Structure of Muscle Terminology Muscle Belly *group of fascicles surrounded by epimysium Fascicles *bundle of muscle fibres *surrounded by perimysium Muscle Fibres *the mega cells *surrounded by the endomysium *made up of contractile elements: **sarcoplasm **myofibrils (made of myofilaments) Contractions *myofilaments: *thin actin filaments move in between thick myosin filaments *myosin filaments do not move **sarcomere: Muscles Arrangments *pennate = orientation and angulation of fascicles Muscle and Joints *a muscle must cross the joint to move it and vice versa **i.e. if a muscle crosses a joint it will move the joint *muscles work at both ends **no origin or insertion end **referred to as proximal and distal attachments Contraction Types *isometric **length of the muscle doesn’t change **no movement **contraction necessary to prevent movement **e.g. holding the body still *isotonic **concentric ***muscle shortens and brings attachment sites closer together **eccentric ***muscle elongates under tension ***force generated must be less than the load ***used for control and precision ***always opposing a concentric contraction ***almost all muscle injuries occur during eccentric contraction The Synovial Joint *diarthroses *most common type *ends of bones (eg. condyles) or special processes (projections) with facets *e.g. articular cartilage **avascular and aneural **nourishment, waste removal and lubrication through synovial fluid (i.e. movement is needed to move the fluid) *synovial Fluid **ultrafiltrate of blood plasma **formed in the synovial membrane ***lines and seals each joint Degeneration of Synovial Joints *fibrillation **“shredding” of articular cartilage *sclerosis **thickening of subchondral bone **in response to increased loading as a result of reduced cartilage function **new “sclerotic” bone is brittle **subchondral sclerosis first sign visible on x-ray *osteophytes **bony outgrowths along the joint margins **often the cause of arthritic pain *joint space narrowing **loss of cartilage = bones closer together *synovitis **inflammation of synovial membrane *eburnation **“polishing” of exposed subchondral bone *subchondral cartilage *subchondral cysts Other Types of Joints Fibrous Joints *synarthroses *sutures **connect flat or irregular shaped bones **permit little or no movement **e.g.: skull *syndesmoses **bind structures together **permit some movement **e.g.: distally in the forearm and leg *gomphoses **one structure “plugged” into another **e.g.: teeth Cartilaginous Joints *amphiarthroses *synchondroses (primary) **hyaline cartilage between bones **epiphyseal (growth) plate **1st sternocostal joint *symphyses (secondary) **fibrocartilaginous joint ***e.g. pubic symphysis **intervertebral joints ***e.g. intervertebral discs Movement of Joints Joint Stability *stability versus mobility Factors Affecting Stability *joint surface shape *active tissue supports **muscle **attachment (muscle/tendon) around joints ***balance (agonist vs antagonist) *degree of congruency with opposing surface *passive tissue supports **capsule **capsular ligaments **non-capsular ligaments